The present invention relates generally to a prefillable delivery device for delivering substances such as drugs, vaccines and the like used in the prevention, diagnosis, alleviation, treatment or cure of diseases, and more specifically relates to a drug delivery device having a needle cannula and a limiter for engaging the surface of the skin and limiting penetration of the tip of the needle cannula into the skin. More specifically, the present invention relates to a limiter capable of fixing the orientation of the needle cannula in a generally perpendicular plane to the skin engaging surface of the limiter and capable of concealing the needle cannula subsequent to administering the intradermal injection.
Intradermal injections are used for delivering a variety of substances. Many of these substances have proven to be more effectively absorbed into or react with the immune response system of the body when injected intradermally. Recently, clinical trials have shown that hepatitis B vaccines administered intradermally are more imunogenic if administered intramuscularly. In addition, substances have been injected intradermally for diagnostic testing, such as, for example using what is known in the art as the xe2x80x9cMantoux testxe2x80x9d to determine the immunity status of the animal against tuberculosis and the immediate hypersensitivity status of Type I allergic diseases.
An intradermal injection is made by delivering the substance into the epidermis and upper layers of the dermis. Below the dermis layer is subcutaneous tissue (also sometimes referred to as the hypodermis layer) and muscle tissue, in that order. There is considerable variation in the skin thickness both between individuals and within the same individual at different sites of the body. Generally, the outer skin layer, epidermis, has a thickness between 50-200 microns, and the dermis, the inner and thicker layer of the skin, has a thickness between 1.5-3.5 mm. Therefore, a needle cannula that penetrates the skin deeper than about 3.0 mm has a potential of passing through the dermis layer of the skin and making the injection into the subcutaneous region, which may result in an insufficient immune response, especially where the substance to be delivered intradermally has not been indicated for subcutaneous injection. Also, the needle cannula may penetrate the skin at too shallow a depth to deliver the substance and result in what is commonly known in the art as a xe2x80x9cwet injectionxe2x80x9d because of reflux of the substance from the injection site.
The standard procedure for making an intradermal injection is known to be difficult to perform, and therefore dependent upon experience and technique of the healthcare worker. This procedure is recommended to be performed by stretching the skin, orienting the bevel of a 26 Gauge short bevel needle cannula upwardly and inserting the needle cannula to deliver a volume of 0.5 ml or less of the substance into the skin of an animal with the needle cannula being inserted into the skin at an angle varying from around 10-15 degrees relative to the plane of the skin to form a blister or wheal in which the substance is deposited or otherwise contained. Accordingly, the technique utilized to perform the standard intradermal injection is difficult and requires the attention of a trained nurse or medical doctor. This procedure also makes it essentially impossible to self-administer an intradermal injection. Inserting the needle to a depth greater than about 3.0 mm typically results in a failed intradermal injection because the substance being expelled through the cannula will be injected into the subcutaneous tissue of the animal. Further, the present method is not suitable for self-administration of intradermal injections.
Further, with the advent of viral infections that are transferred through contact with bodily fluids, it is desirable to enclose a needle cannula subsequent to administering an injection. Preferably, a needle assembly should include a mechanism that is capable of enclosing a needle cannula immediately subsequent to administering the injection. If a needle is left uncovered for even a short period of time after administering an injection, such as, for example, while trying to reattach a needle cap, a biohazard exists. U.S. patent application Ser. No. 09/417,671 discloses needle assemblies having a limiter to facilitate administering an intradermal injection, the disclosed assemblies are not capable of concealing or enclosing the needle cannula after administering the injection. Therefore, it is desirable to provide a needle assembly with an integral device that is simply designed, easy to use, and readily available immediately after administering an injection.
Accordingly, there has been a need for a needle assembly of intradermal injection device providing the ability to perform an intradermal injection of substances which overcomes the problems and limitations associated with conventional needle assemblies. Further, there has been a need to provide the needle assembly with an enclosure device that is capable of enclosing a needle cannula immediately subsequent to administering the intradermal injection. The combination of these two features on the same needle assembly would provide the ability to both reduce the probability of error and pain caused from the intradermal injection and to enclose the needle cannula after the injection has been administered.
In contrast to the needle assemblies discussed above, the present invention both enables the administration of an intradermal injection utilizing a simplified method that reduces the probability of error and also enables the user to conceal the needle immediately after administering the injection. Specifically, The prefillable intradermal injector of the present invention for use in intradermally injecting substances into the skin of an animal includes a prefillable reservoir adapted to store a substance and having an outlet port at a first end enabling the substance to be expelled from the reservoir and a stopper in a second open end, a needle cannula defining an axis and the needle cannula in fluid communication with the reservoir to receive the substance from the outlet port and having a forward tip adapted to penetrate the skin of an animal, a limiter surrounding the needle cannula, the limiter including a generally flat skin engaging surface extending in a plane generally perpendicular to an axis of the needle cannula, and a sleeve having a first end and a second end, the sleeve surrounding and slidable relative to the reservoir along the axis and the sleeve fixed relative to the stopper whereby movement of the sleeve causes the stopper to move through the reservoir to expel the substance from the reservoir through the needle cannula.
In the preferred embodiment of the prefillable intradermal injector, the limiter is moveable axially relative to the needle cannula from a retracted position wherein the forward tip of the needle cannula extends through the limiter to an extended position wherein the needle cannula forward tip is enclosed within the limiter. Also, the forward tip of the needle cannula extends through the limiter beyond the skin engaging surface no more than from about 0.5 mm to about 3.0 mm in the retracted position of the limiter.
In addition, in the preferred embodiment, the limiter is moveable axially relative to the reservoir from a first position wherein the forward tip of the needle is located within the limiter to a second position wherein the needle extends through the limiter beyond the skin engaging surface no more than from about 0.5 to 3.0 mm, with the limiter including an axial opening therethrough receiving the forward tip of the needle cannula and the opening includes pierceable insert sealing the axial opening, and the forward tip of the needle cannula preferably extending beyond the skin engaging surface no more than from about 1.0 to 2.0 mm, and more preferably extending beyond the skin engaging surface about 1.5 mmxc2x10.2 to 0.3 mm. Also, the forward tip of the needle cannula pierces the insert when the limiter is located in the second position thereby exposing the forward tip enabling administration of the intradermal injection.
Also, in the preferred embodiment, the limiter includes a locking arm and the sleeve includes a catch engaging the locking arm when the limiter is located in the extended position enclosing the forward tip of the needle cannula, with the locking arm including a hook disposed upon a distal end and the catch includes a slot disposed in the sleeve and the hook engaging the slot when the limiter is located in the extended position. Further, the prefillable container includes a stop to terminate movement of the limiter at the second position when moving the limiter between the first position and the second position. Still further, the prefillable intradermal injector includes a spring biasing the limiter to move from the retracted position to the extended position, with the spring preferably coiled around the reservoir. The sleeve includes a stopper engaging portion, with stopper engaging portion including a plunger rod operably connected to the second end of the sleeve.
The method of the present invention for administering an intradermal injection through a needle cannula from a prefillable intradermal injector having a substance stored in a reservoir in fluid communication with a needle cannula defining an axis, includes the steps of providing a limiter slideably disposed on the reservoir and having a generally flat skin engaging surface extending in a plane generally perpendicular to the axis of the needle cannula having a forward tip located within the limiter, moving the limiter in a first direction relative to the reservoir to expose the forward tip, expelling the substance from the reservoir through the needle cannula into the skin of an animal, and moving the limiter in a second direction relative to the reservoir to enclose the forward tip inside the limiter.
In the preferred embodiment of the method, moving the limiter in the first direction includes piercing an insert centrally located within the limiter, and depressing the skin engaging surface against the skin of the animal inserts the forward tip into the skin of the animal. In addition, the method includes locking the forward tip inside the limiter after administering the intradermal injection, with locking the forward tip inside the limiter further defined by locking the limiter in a position relative to the prefillable container. Also, the limiter limits penetration of the forward tip of the needle cannula into the dermis layer of the skin during the step of moving the limiter in the first direction, with penetration of the forward tip of the needle cannula limited to about 0.5 to 3.0 mm, and preferably limited to about 1.0 to 2.0 mm or 1.5 mmxc2x10.2 to 0.3 mm.
Alternatively, the prefillable intradermal injector of the present invention includes a reservoir prefillable with a substance having a generally closed proximal end and an open distal end, a needle cannula having a distal end in fluid communication with the substance in the reservoir extending through the proximal end and an exposed forward tip, a stopper slideably received in the open distal end of the reservoir moveable in the reservoir to expel the substance through the forward tip of the needle cannula, and a limiter having a distal end slideably supported around the reservoir and moveable relative to the reservoir and a generally closed proximal end including a flat skin engaging surface having an opening therethrough receiving the forward tip of the needle cannula therethrough as the limiter moves relative to the reservoir and the limiter limiting extension of the forward tip of the needle cannula beyond the skin engaging surface a distance of more than 3.0 mm.
In this embodiment of the prefillable intradermal injector, the proximal end of the reservoir engages a surface of the limiter as the limiter is moved toward the reservoir, thereby limiting movement of the limiter relative to the reservoir. In addition, the intradermal injector includes a sleeve surrounding the reservoir operably fixed to the stopper whereby movement of the sleeve relative to the reservoir moves the stopper through the reservoir. Also, the opening through the proximal end of the limiter includes a pierceable closure and the forward tip of the needle cannula pierces the closure as the limiter is moved toward the reservoir, with the forward tip of needle cannula extends through the limiter beyond the skin engaging surface no more than from about 1.0 to 2.0 mm, and preferably 1.5xc2x10.2 to 0.3 mm. Further, the intradermal injector includes a spring biased between the reservoir and the limiter moving the limiter to an extended position enclosing the forward tip of the needle cannula following injection.
The present invention provides the desirable features set forth above that are not presently included on the same needle assembly. The limiter facilitates making an intradermal injection at a generally perpendicular angle to the skin of the animal and then also conceal or enclose the needle subsequent to administering the injection.